The human anatomy includes many types of tissues that can either voluntarily or involuntarily, perform certain functions. After disease, injury, or natural defects, certain tissues may no longer operate within general anatomical norms. For example, organs such as the heart may begin to experience certain failures or deficiencies. Some of these failures or deficiencies can be diagnosed, corrected or treated with implantable medical devices (IMDs), such as heart monitors, pacemakers, implantable cardioverter-defibrillators (ICDs), myostimulators, nerve stimulators, drug delivery devices, subcutaneous defibrillators, and several other known IMDs.
IMDs for monitoring a physiological condition or delivering a therapy typically rely on one or more sensing element such as sensors and/or electrodes positioned in a patient's blood vessel, heart chamber, or other portion of the body. Raw signals relating to a physiological condition from which a patient condition or the need for therapy can be assessed are generally sensed by the sensing element. The raw signals are typically transmitted to the IMD for processing through implantable medical electrical lead(s) associated with the sensing element. In other types of IMDs or implantable systems, additional leads may be used for applying a therapy stimulus to various body areas such as the spinal column. These leads typically include a lead body extending between a proximal lead end and a distal lead end and the sensing element is typically incorporated on or along the length of the lead such as near the distal end.
Implantable medical leads can extend from a subcutaneous implantation site of the IMD through an internal body pathway to a desired tissue site. The leads are generally preferred having small diameter, highly flexible, lead bodies that withstand degradation by body fluids and body movements that apply chemical or physical stress and strain to the lead body and the connections made to sensing element. As lead bodies are made smaller and smaller and the number of lead conductors is increased or maintained, the integrity of lead conductors and insulators is increasingly important.
Various studies indicate that an implanted lead may degrade for one or more reasons. For example, a study by Dorwarth et al., “Transvenous defibrillation leads: high incidence of failure during long-term follow-up,” J Cardiovasc Electrophysiol., 14(1):38-43 (2003), found that a majority of lead-related sensing failures were associated with insulation defects that occurred late after ICD placement (6.0+/−1.8 years after implant). Dorwarth et al. observed that “automated device control features with patient alert function integrated into new devices may contribute to early detection of lead failure.”
As described herein, the present disclosure addresses the need in the art for mechanisms that support early detection of a lead-related condition and or graceful degradation in the emergence of a lead-related condition.